This invention relates in general to fixtures for mounting castings for vehicle wheels on machine tools during finishing operations and in particular to a chuck for mounting a wheel casting upon a wheel lathe for machining the casting to final shape.
Light weight alloy vehicle wheels are becoming increasingly popular. Such wheels typically include an annular wheel rim which carries a tire. A circular wheel disc is formed across one end of the wheel rim. The wheel disc usually includes a central hub portion supported within the wheel rim by a plurality of wheel spokes. A central pilot hole and plurality of wheel mounting holes are formed through the wheel hub.
One conventional process for manufacturing light weight alloy wheels involves pouring molten metal into a wheel mold to form a casting of the wheel. After the molten metal solidifies, the wheel casting is removed from the mold. The wheel casting is oversized and is machined to final shape. Alternately, a full face wheel disc which includes the outboard tire bead retaining flange is cast from a light weight alloy and machined to final shape. A partial wheel rim, which can be rolled from a strip of steel, is then welded to an inboard surface of the wheel disc to form a two piece wheel. Such a wheel combines the low cost and strength of a steel rim with a pleasing aesthetic appearance of a wheel disc cast from a light weight metal and is usually referred to as a bimetal wheel.
Machining the wheel or wheel disc casting typically includes multiple operations. Sawing machines cut any casting gates and risers from the wheel casting. A drilling machine is used to drill the wheel mounting holes through the wheel hub. The wheel casting is then mounted upon a wheel lathe for machining to its final shape. During the lathe operations, the inside surface of the wheel hub is usually faced to provide a flat mounting surface. Similarly, the outboard wheel hub surface is faced and both the inside and outside of the wheel rim are turned to their final shapes. The central pilot hole is usually drilled while the casting is clamped in the lathe for turning the inboard tire bead seat.
Referring now to the drawings, there is shown generally at 10 in FIG. 1 a sectional view of a prior art chuck for clamping a wheel casting on a wheel lathe (not shown). The chuck 10 includes a cylindrical riser adapter 11 which is attached to the rotatable spindle of a wheel lathe (not shown) by conventional means. The riser adapter 11 supports a circular face plate 12. The face plate 12 has a center opening 13 formed therethrough which receives a generally cylindrical center assembly 14. The center assembly carries a plurality of locator pylons 15 (one shown) which position a wheel casting 16 upon the chuck 10. The face plate 12 also carries a plurality of part rests 17 (one shown) which are attached about the circumference thereof. A plurality of slots 18 (one shown) are formed in the outer edge of the face plate 12 and extend inward in a radial direction.
An actuator rod 20 extends axially into the riser adapter 11. A circular yoke plate 21 is disposed within the riser adapter 11 and attached to the end of the actuator rod 20. A plurality of guide pins 22 (one shown) extend between the riser adapter 11 and the face plate 12 and pass through apertures formed in the yoke plate 21. The actuator rod 20 and yoke plate 21 are movable in an axial direction by a conventional mechanism (not shown). A plurality of external arms 23 (one shown) are pivotally mounted upon tabs which extend radially from the circumference of the yoke plate 21. A generally L-shaped arm guide slot 24 extends through each arm 23. A first end of each arm 23 is received by an associated face plate arm slot 18. An arm guide pin 25 extends transversely through the arm guide slot 24. A jaw insert 26 is secured to a second end of each of the arms 23.
During the machining operations, the actuator rod 20 and yoke plate 21 are moved to the right in FIG. 1. As the yoke plate 21 moves, the arm guide slots 24 cooperate with the arm guide pins 25 to urge the arms 23 and jaw inserts 26 in an outward radial direction, thereby opening the chuck 10. The wheel casting 16 is then placed on the locator pylons 15 and the actuator rod 20 and yoke plate 21 are moved to the left in FIG. 1. As the yoke plate 21 moves, the arm guide slots 24 cooperate with the arm guide pins 25 to urge the arms 23 and jaw inserts 26 in an inward radial direction, closing the chuck 10 upon the wheel casting 16. The jaw inserts 26 cooperate with the part rests 17 to clamp the wheel casting 16 in the chuck 10.